Restatement of Consolidated Financial Statements, Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Jul. 31, 2018	Jul. 31, 2017
Current assets [Abstract]
Cash and cash equivalents	$ 13,496	$ 12,858
Investment securities available for sale	1,497	1,498
Contract receivables, net	25,615	30,949
Income tax receivable	1,230	1,601
Other current assets	1,752	2,078
Total current assets	43,590	48,984
Property, buildings and equipment, net	3,870	4,277
Deferred income taxes	789	853
Equity Method Investments	2,058	1,463
Other assets	2,522	2,340
Total assets	52,829	57,917
Current liabilities [Abstract]
Accounts payable	5,635	7,771
Lines of credit	0	372
Accrued payroll costs	6,066	5,976
Current portion of long-term debt and capital lease obligations	54	382
Billings in excess of revenue	3,191	2,607
Other accrued liabilities	1,382	1,974
Total current liabilities	16,328	19,082
Income taxes payable	0	31
Deferred income taxes	0	4
Long-term debt and capital lease obligations	54	66
Shareholders' equity [Abstract]
Preferred stock	0	0
Capital in excess of par value	17,558	17,570
Retained earnings	20,973	23,005
Accumulated other comprehensive loss	(1,885)	(1,795)
Treasury stock, at cost	(907)	(1,037)
Total Ecology and Environment Inc. shareholders' equity	35,783	37,787
Noncontrolling interests	664	947
Total shareholders' equity	36,447	38,734
Total liabilities and shareholders' equity	52,829	57,917
Class A [Member]
Shareholders' equity [Abstract]
Common stock	30	30
Class B [Member]
Shareholders' equity [Abstract]
Common stock	$ 14	14
As Previously Reported [Member]
Current assets [Abstract]
Cash and cash equivalents		13,343
Investment securities available for sale		1,498
Contract receivables, net		35,107
Income tax receivable		1,293
Other current assets		2,119
Total current assets		53,360
Property, buildings and equipment, net		4,428
Deferred income taxes		1,203
Equity Method Investments		0
Other assets		1,786
Total assets		60,777
Current liabilities [Abstract]
Accounts payable		8,073
Lines of credit		581
Accrued payroll costs		6,338
Current portion of long-term debt and capital lease obligations		382
Billings in excess of revenue		2,850
Other accrued liabilities		2,645
Total current liabilities		20,869
Income taxes payable		31
Deferred income taxes		3
Long-term debt and capital lease obligations		66
Shareholders' equity [Abstract]
Preferred stock		0
Capital in excess of par value		17,608
Retained earnings		23,509
Accumulated other comprehensive loss		(2,018)
Treasury stock, at cost		(1,037)
Total Ecology and Environment Inc. shareholders' equity		38,106
Noncontrolling interests		1,702
Total shareholders' equity		39,808
Total liabilities and shareholders' equity		60,777
As Previously Reported [Member] | Class A [Member]
Shareholders' equity [Abstract]
Common stock		30
As Previously Reported [Member] | Class B [Member]
Shareholders' equity [Abstract]
Common stock		14
GAC Deconsolidation Adjustments [Member]
Current assets [Abstract]
Cash and cash equivalents		(208)
Investment securities available for sale		0
Contract receivables, net		(4,066)
Income tax receivable		308
Other current assets		113
Total current assets		(3,853)
Property, buildings and equipment, net		(151)
Deferred income taxes		0
Equity Method Investments		1,272
Other assets		408
Total assets		(2,324)
Current liabilities [Abstract]
Accounts payable		(361)
Lines of credit		(209)
Accrued payroll costs		(362)
Current portion of long-term debt and capital lease obligations		0
Billings in excess of revenue		(243)
Other accrued liabilities		(671)
Total current liabilities		(1,846)
Income taxes payable		0
Deferred income taxes		56
Long-term debt and capital lease obligations		0
Shareholders' equity [Abstract]
Preferred stock		0
Capital in excess of par value		(9)
Retained earnings		7
Accumulated other comprehensive loss		223
Treasury stock, at cost		0
Total Ecology and Environment Inc. shareholders' equity		221
Noncontrolling interests		(755)
Total shareholders' equity		(534)
Total liabilities and shareholders' equity		(2,324)
GAC Deconsolidation Adjustments [Member] | Class A [Member]
Shareholders' equity [Abstract]
Common stock		0
GAC Deconsolidation Adjustments [Member] | Class B [Member]
Shareholders' equity [Abstract]
Common stock		0
Out of Period Adjustments [Member]
Current assets [Abstract]
Cash and cash equivalents		(277)
Investment securities available for sale		0
Contract receivables, net		(92)
Income tax receivable		0
Other current assets		(154)
Total current assets		(523)
Property, buildings and equipment, net		0
Deferred income taxes		(350)
Equity Method Investments		191
Other assets		146
Total assets		(536)
Current liabilities [Abstract]
Accounts payable		59
Lines of credit		0
Accrued payroll costs		0
Current portion of long-term debt and capital lease obligations		0
Billings in excess of revenue		0
Other accrued liabilities		0
Total current liabilities		59
Income taxes payable		0
Deferred income taxes		(55)
Long-term debt and capital lease obligations		0
Shareholders' equity [Abstract]
Preferred stock		0
Capital in excess of par value		(29)
Retained earnings		(511)
Accumulated other comprehensive loss		0
Treasury stock, at cost		0
Total Ecology and Environment Inc. shareholders' equity		(540)
Noncontrolling interests		0
Total shareholders' equity		(540)
Total liabilities and shareholders' equity		(536)
Out of Period Adjustments [Member] | Class A [Member]
Shareholders' equity [Abstract]
Common stock		0
Out of Period Adjustments [Member] | Class B [Member]
Shareholders' equity [Abstract]
Common stock		$ 0